Ret/PTC Activation in Benign and Malignant Thyroid Tumors Arising in a Population Exposed to Low-Dose External-Beam Irradiation in Childhood

Ionizing radiation is the strongest risk factor known for the development of thyroid neoplasia. Although ret/PTC rearrangements have been identified in both spontaneous and radiation-induced papillary thyroid cancer, they seem more frequent among radiation-associated tumors. We studied the frequency of ret/PTC activation in a group of sporadic and radiation-induced thyroid carcinomas (n = 49) and adenomas (n = 13) among 44 individuals treated for Tinea Capitis with low-dose external irradiation as well as in 18 nonirradiated subjects. Total RNA recovered from paraffin-embedded thyroid cancer surgical specimens was analyzed for ret/PTC 1, 2, and 3 mutations using RT-PCR with Southern blotting to maximize detection sensitivity. Ret/PTC rearrangements were identified in 42.9% of thyroid carcinoma and 46.2% of adenoma subjects. Among the positive carcinoma specimens, three were follicular carcinomas. Ret/PTC 1, the predominant rearrangement, was more prevalent in nonirradiated compared with irradiated carcino...